Prothioconazole, 2-[(2RS)-2-(1-chlorocyclopropyl)-3-(2-chlorophenyl)-2-hydroxypropyl]-2H-1,2,4-triazole-3(4H)-thione, the structure of which is shown below, is used as a fungicide to treat infected crops. The molecule itself was first described in U.S. Pat. No. 5,789,430 and corresponding patent publications. Two crystalline forms of prothioconazole, named Form I and Form II, are disclosed in U.S. Pat. No. 5,789,430 and U.S. Patent Publication No. 2006/0106080, respectively. The contents of both of these U.S. patent publications are incorporated herein by reference. Form I is described in the '080 publication as being metastable at room temperature and Form II is described therein as being thermodynamically stable at room temperature.

Prothioconazole structure is described in M. Jautelat et al., Pflanzenschultz-Nacbrichten Bayer, 57/2004, 2, 145-162.
Different crystalline forms of commercially important molecules, including amorphous forms and crystalline solvates, often possess different properties, which may be useful in different contexts. Thus, for example, crystalline forms are generally more stable than amorphous forms, making them useful for long-term storage of the solid material, whereas amorphous forms are often more readily soluble than crystalline forms and may thus be more useful for administration than crystalline forms for certain purposes.
The crystal form of a compound affects its physico-chemical properties, such as melting point, solubility, or dissolution rate. It is therefore advantageous that crystal forms with a range of lattice energies, and hence a range of physico-chemical properties be available, so as to allow for example the effectiveness of treatment (e.g. agricultural (such as plant treatment), veterinary or medicinal treatment) to be optimized. Thus for example a more stable, but less soluble form may be advantageous in some applications, whereas a higher energy, more soluble form may provide a different set of advantages in other applications.
Since prothioconazole is a microbicidal active agent, it is highly desirable to obtain new forms having improved solubility and/or dissolution rate.
Such new forms of prothioconazole may require lower dosage, reduce application rate, as compared to crystalline less soluble forms. Such new forms may have the particular advantages of inter alia having for example improved knock down effect as a result of the higher solubility and dissolution rate.
The amorphous form of solids is often characterized by a lower physical stability, sometimes accompanied by hygroscopic behavior, agglomeration, and other such changes. Additionally processing of amorphous powder is often difficult because of its instability. Much of this behaviour is a result of the normally small particle size, typically only a few microns. Therefore it will be advantageous to be able to influence the particle size of an amorphous material, in order to optimize it for different properties and applications. Further, it will be advantageous to obtain an amorphous form having relatively high particle size diameter.
Solid state chemistry of a crystal cannot predict whether an organic solvent can incorporate into the crystal. The manner in which solvation of a crystal may occur is also unpredictable. There are no rules that allow prediction of whether a compound will exist as solvated form of an organic solvent.
The discovery of new forms such as solvated form and amorphous form of for example an agriculturally, veterinary or medicinally useful compound may provide an opportunity to improve the performance characteristics of a product. It enlarges the repertoire of materials that a formulation scientist has available for designing, for example, a dosage form of a compound with a targeted release profile or other desired characteristic. It is clearly advantageous when this repertoire is enlarged by the discovery of new solvated crystalline forms or amorphous forms of a useful compound. Thus it will be advantageous to have new solvated crystalline forms or amorphous forms of prothioconazole, and efficient methods for their preparation.